Q. We are an aluminum wheel repair facility using urethane paints on our reconditioned
wheels. All machined wheels are pre-treated with PPG product DX-501 before spraying
with clear. Will it hold up as well as powder and be durable? What are th pros
and cons with powder coating?

Clear liquid polyurethane coatings are used quite extensively in the automotive
industry. They're primarily used as the clear coat, top coat found on most cars
and are formulated to be very durable. Clear powder coatings have not yet gained
recognition in this area primarily due to aesthetic reasons. Clear powder coatings
are used quit extensively by automotive wheel manufacturers, are durable and
can be very cost-effective.

You don't tell me what your processes are, I will assume that the wheels are
liquid coated then removed from the spray area, and allowed to air dry. The
equipment expense involved for this type of application is minimal in comparison
to the equipment needed for powder coating applications.

Powder coating application requires special electrostatic spray guns, and an
oven to melt and cure the powder. Powder coatings have many advantages over
liquid coating systems. Some of the primary ones are: Low VOC emissions (essentially
none) Low toxicity and flammability, No solvent needed in application, Wide
variety of colors, glosses, and textures.

Powder coatings also have limitations. Some are these are: High baking temperatures
325-400 degrees F, oven-curing restricts it to shop use, color change is labor
intensive (costly), atomized powder in air may be explosive, initial equipment
expense.

As with the liquid polyurethane coating system, the aluminum surface must be
very clean, and free of any dirt, oil, or grease. The use of an aluminum pre-treatment
or conversion coating is always recommended to promote good adhesion and provide
good corrosion resistance. I recommend that you contact a local powder coating
representative and discuss the possibilities of converting to a powder coating
system.